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Negative predictive value of a vision screening program aimed at children aged 3 to 4 years old
Lica Chui1, Tara Fraser, Karen Hoar
1Department of Ophthalmology, Dalhousie University, Halifax, Nova Scotia, Canada.
Purpose:
Nova Scotia has a vision screening program which assesses children aged 4[1\2] to 5[1\2] years. However, its use in younger children proved impossible. This study will examine a modified screening protocol for the younger children (3 to 4 years old) and determine its negative predictive value and minimum age for reliable application.
Materials And Methods:
Public health nurses administered the study protocol to 3- to 4-year-old children. One hundred seventy-eight children were screened over two summers. Medical and family history, external inspection, as well as measures of visual acuity with the Lea Hyvarinen symbols chart and stereoacuity with Frisby plates were recorded. Results were compared with a gold standard examination that included full orthoptic and ophthalmologic evaluations. One hundred forty-one (79%) children underwent the gold standard examination. Agreement between screening and gold standard examinations was studied.
Results:
Data showed increased concordance between screening and gold standard examination results with increasing age up to 41 months. Negative predictive value (NPV) and specificity also improved when data were separated by this age. In children <41 months old, the screening test NPV was 90%, specificity, 68%, and sensitivity, 75%. In comparison, children >/=41 months old had screening test NPV of 96%, specificity, 95%, and sensitivity, 50%. Specificity was higher in the older age group ( P < 0.001). Sensitivity was lower ( P = 0.004).
Conclusion:
This study's vision screening protocol appears better suited for children 41 months and older. They had better pass/fail reproducibility than children <41 months. The test's simplicity allows easy use by non-eye-care professionals. It could potentially lower the reliable screening age of children by 13 months, from 54 months of age (4[1\2] years old) to 41 months. This screening may miss some refractive errors and microtropia/monofixation syndrome, despite normal visual acuity, stereoacuity, and external inspection.
